Description

• A trojan virus looks like a useful application, and may actually be housed inside a working program that performs a useful function. The program attempts to trick a user into installing the malware or allowing the malware to access the system by claiming to perform some other function.
  
  

Techniques

• Trojans commonly take the guise of toolbars, though any program could theoretically contain trojan malware. Other common trojans claim to be antivirus software, computer scanning software, games or joke email attachments.
  
  

Types

• A trojan often installs adware on the host computer, forcing the user to view pop-up or banner advertisements. It may also contain a virus that destroys files, self-replicates and eats system memory, or spyware that monitors the user's behavior.
  
  

Security

• Antivirus programs guard against trojans in addition to other malicious software, but user discretion also plays a part in keeping your computer clean. Double-check the legitimacy of downloaded software and email attachments before executing.
  
  

Other Malware

• Trojans differ from other malware, such as worms and bots, though a trojan may contain these items as part of its delivery system.